1. Field of the Invention
The present invention relates to an electronic calculator having an auxiliary display screen and a method for controlling the electronic calculator.
2. Description of the Related Art
Desktop electronic calculators have been devised each of which includes two numeral display areas, upper and lower, in which a tax inclusive amount and a tax exclusive amount are displayed in comparison with each other as a result of calculation (see patent document 1, for example).
Calculating devices have been devised in which a plurality of currencies, such as euros and dollars, are displayed in parallel in different rows and when an arbitrary currency is designated and its numerical value is input, the currency is converted on the basis of the input numerical value and the converted currency amount is displayed (see patent documents 2 and 3, for example).
3. Patent Documents                Patent Document 1: Jpn. Pat. Appln. KOKAI Publication No. 2001-109721        Patent Document 2: Jpn. Pat. Appln. KOKAI Publication No. 2000-315195        Patent Document 3: Jpn. Pat. Appln. KOKAI Publication No. 2000-311142        
In conventional calculating devices, a user was able to display a plurality of converted currency amounts in parallel, whereas the user was not able to confirm a conversion rate or designate a conversion transition (e.g., [$→¥ (multiplication)] and [¥→dollar (division)]) by a simple operation in the conversion process.
In particular, when a plurality of conversion rates are used, it was difficult for the user to know which of the conversion rates is used to perform a conversion process.